I think there may be a significant difference between those people who are "early onset" from those who are "late onset". I have the impression from participating in various PD online support groups.... that , generally speaking, you have 4 or 5 years at best with Carbidopa Levodopa (Sinemet) before you have to augment it with other drugs and it becomes less and less effective. I wish that people would clarify which Subtype of they are (early onset or late) ... as they are significantly different in longevity, effectiveness of particular drugs, incidence of dementia, etc.